The invention relates to stabilized o-iodoxybenzoic acid, or IBX, compositions of the formula 
and to a process for the preparation thereof.
This hypervalent iodine derivative is the precursor of 1,1,1-triacetoxy-1,1-dihydro-1,2-benzodioxol-3(1H)-one or periodinane of Dess-martin, of the Formula 
which was described for the first time in J. org. Chem. 1983, 48, 4155-4156 as a gentle and selective oxidizer of primary and secondary alcohols into carbonyl compounds.
Despite that important property, the risks run during the handling of that reagent and its precursor, IBX, hinder their marketing and even their use in chemical synthesis, beyond the laboratory stage.
Those two compounds decompose violently, as mentioned by J. B. Plumb and D. J. Harper in Chemical, and Engineering News, p3, Jul. 16, 1990 or in J. Org. Chem. 1993, 58, 2899, which article describes an improved process for the preparation of Dess-Martin periodinane starting from IBX.
IBX can be prepared by oxidizing 2-iodobenzoic acid, especially with KBrO3 in sulfuric acid, this being a usual process which has been improved several times, or with Oxone(copyright), consisting of 2KHSO5,KHSO4,K2SO4, as described in J. Org. Chem. 1999, 64, 4537-4538. The authors of this recent article confirm that the IBX obtained is a white crystalline solid which explodes even when in very pure form.
The applicant has himself established that Dess-Martin periodinane decomposes violently at its melting temperature and that IBX, even when moistened with water or acetic acid, has explosive properties when it is subjected to the action of heat in accordance with method A14 of Directive 92/69/EEC.
It was therefore desirable to find a means of stabilizing o-iodoxybenzoic acid as soon as it has been prepared in order to enable it to be used in organic synthesis without major risk.
Sorbitol, which was proposed 50 years ago in U.S. Pat. No. 2,566,592 as an agent for stabilizing IBX and its calcium and ammonium salts in order to permit their use in therapeutics, does not really appear to be efficient and, above all, it is not suitable when IBX has to be used in a reaction for oxidizing alcohols.
The applicant has now found other agents for stabilizing IBX which do not hinder its use as an oxidizing agent, and the composition comprising a suitable amount of at least one of those agents and IBX no longer explodes under the action of impact or a major increase in temperature, so that this periodinane can be used more widely in synthesis, especially instead of the Dess-Martin reagent.
M. Frigerio, M. Santogostino, S. Sputore and G. Palmisano have reported in J. Org. Chem. 1995, 60, 7272-7276 that IBX, whose insolubility in numerous organic solvents and in water limited its use, had, in solution in dimethyl sulfoxide, oxidizing properties comparable to those of the Dess-Martin reagent, without exhibiting the latter""s sensitivity to moisture which was reported, in particular, in J. Org. Chem. 1994, 59, 7549-7552.
By way of example of that use, there may be mentioned in addition to the reactions described by M. Frigerio et al. those resulting from the work of K. C. Nicolaou et al., which is described, in particular, in Angew. Chemie, Int. Ed. 2000, 39, 625-628 and 2525-2529 or, in the case of anilides, in Angew. Chemie 2000, 112(3), 639-642.
It has now been found that those reactions could be carried out in polar aprotic solvents other than dimethyl sulfoxide when using the stabilized compositions of the invention, especially in tetrahydrofuran or N-methylpyrrolidone.
The present invention relates to stabilized o-iodoxybenzoic acid compositions that comprise, for one mole of o-iodoxybenzoic acid, from 0.5 to 4 moles of a stabilizing agent selected from the group consisting of:
aliphatic acids of formula I
CH3(CH2)nCOOH
in which n is from 8 to 20 and preferably equal to 14 or 16, and mixtures thereof,
benzenecarboxylic acids of formula II 
xe2x80x83in which R represents H, CH2, COOH and mixtures thereof
and mixtures of acids of formula I and II.
Preference is given to compositions in which there are from 1 to 2.5 moles of stabilizing agent per mole of o-iodoxybenzoic acid and especially from 1.8 to 2.2 moles, in order to ensure maximum stabilisation without increasing costs excessively.
Of the acids of formula II, preference is given to benzoic, toluic, isophthalic and terephthalic acids and, of those, to the acids having melting points higher than 200xc2x0 C., such as isophthalic acid and terephthalic acid, which temperature is generally acknowledged to be that at which IBX explodes spontaneously.
However, mixtures of benzoic acid or o-toluic acid or a mixture thereof, on the one hand, and of isophthalic acid or terephthalic acid or a mixture thereof, on the other hand, at the rate of from 25 to 75 mole % of the monoacid in the mixture and preferably from 45 to 55%, give stabilized compositions that do not explode under the action of impact or heat.
Iodoxybenzoic acid compositions comprising one or more compounds of formula II as the stabilizing agent are preferred.
It is preferable in compositions based on a stabilizing agent of formula I also to introduce an agent of formula II and preference is given to mixtures of, on the one hand, stearic acid or palmitic acid or a mixture thereof, which are widely available acids, and, on the other hand, terephthalic acid or isophthalic acid or a mixture thereof, at the rate of from 25 to 75 mole t of fatty acid in the mixture.
The invention relates also to the process for the preparation of the compositions of the invention, either starting from IBX that has already been isolated or during the synthesis of IBX.
In order to prepare a composition starting from IBX that has already been isolated or in order to homogenise a composition of the invention, a solution or suspension in water of the alkali salts, particularly of sodium, of the acids constituting the composition is prepared and then the solution or suspension is acidified until the composition has been rendered completely insoluble.
It is possible either to add a solution of an alkali hydroxide to the suspension of the component acids in water or to add said acids to an aqueous alkali hydroxide solution in a sufficient amount.
It is also possible to introduce preferably all or part of a suitable amount of one of the stabilizing agents of formula I or II, one of its alkali salts or a mixture thereof into the medium in which the IBX is prepared, as soon as the reaction starts, if the stabilizing agent is not decomposed in that reaction medium. When the stabilizing agent is a mixture, one of the components can be added in the course of the reaction and the other can be added before the IBX is isolated.
The person skilled in the art can determine in a few preliminary tests the relative proportions of the stabilizing agent(s) and of IBX and also the methods of introducing those agents, taking into account their possible reactivity and their relative solubilities in the reaction and precipitation media.